KR20190134325A - Silicon based melting composition and manufacturing method for silicon carbide single crystal using the same - Google Patents

Abstract

According to an embodiment of the present invention, a silicon-based molten composition is used in a solution growing method for forming a silicon carbide single crystal, comprises silicon (Si), yttrium (Y) and iron (Fe) and is represented by chemical formula (1): Si_aY_bFe_c. In the chemical formula (1), a is more than or equal to 0.4 and less than or equal to 0.8; b is more than or equal to 0.15 and less than or equal to 0.5; and c is more than or equal to 0.05 and less than or equal to 0.3.

Description

Silicon-based melt composition and a method for producing silicon carbide single crystal using the same {SILICON BASED MELTING COMPOSITION AND MANUFACTURING METHOD FOR SILICON CARBIDE SINGLE CRYSTAL USING THE SAME}

The present invention relates to a silicon-based melt composition and a method for producing silicon carbide single crystals using the same.

Power semiconductor devices are key devices in next-generation systems that use electric energy, such as electric vehicles, power systems, and high-frequency mobile communications. To do this, it is necessary to select materials suitable for high voltage, high current, and high frequency. Silicon single crystals have been used as power semiconductor materials, but due to physical limitations, silicon carbide single crystals, which have low energy loss and can be driven in more extreme environments, are drawing attention.

For the growth of silicon carbide single crystals, for example, silicon carbide is used as a raw material to sublimate at a high temperature of 2000 ° C. or higher to grow single crystals, a sublimation method using a crystal pulling method, and a chemical method using a gas source. A vapor deposition method or the like is used.

Chemical vapor deposition can be used to grow to a limited thin film level, and sublimation can cause defects such as micro-pipes and stacking defects, resulting in limited production costs. The research on the solution growth method is known that the crystal growth temperature is lower than the sublimation method and is known to be advantageous for large diameter and high quality.

The present invention is to provide a silicon-based melt composition capable of a stable crystal growth process for a long time while suppressing the precipitation of impurities. It is also an object of the present invention to provide a silicon-based melt composition capable of providing silicon carbide single crystal of high quality. It is also an object of the present invention to provide a method for producing silicon carbide single crystals using the silicon-based melt composition.

In addition, the technical problem to be solved by the present invention is not limited to the above-mentioned technical problem, and other technical problems not mentioned are clearly to those skilled in the art from the following description. It can be understood.

The silicon-based melt composition for achieving the above-mentioned problems is used in the solution growth method for forming silicon carbide single crystal, and contains silicon (Si), yttrium (Y) and iron (Fe) and is represented by the following formula (1): .

Si _a Y _b Fe _c (Equation 1)

In Formula (1), a is 0.4 or more and 0.8 or less, b is 0.15 or more and 0.5 or less, and c is 0.05 or more and 0.3 or less.

In one embodiment, a method of preparing silicon carbide single crystals may include preparing a silicon carbide seed crystal, comprising silicon (Si), yttrium (Y), and iron (Fe), and using a silicon-based melt composition represented by the following formula (1): Preparing, forming a melt containing the silicon-based melt composition and carbon (C), and obtaining a silicon carbide single crystal on the silicon carbide seed crystal from the melt.

Si _a Y _b Fe _c (Equation 1)

In Formula (1), a is 0.4 or more and 0.8 or less, b is 0.15 or more and 0.5 or less, and c is 0.05 or more and 0.3 or less.

In the step of obtaining the silicon carbide single crystal, yttrium silicide may not be precipitated.

Forming the melt may include charging the silicon-based melt composition in a crucible and heating it.

The heating may include heating the melt to 1800 degrees (° C.).

The melt may have a saturated carbon solubility.

After forming a temperature gradient of −20 ° C./cm based on the surface of the melt, the silicon carbide seed crystals may contact the surface of the melt.

The growth rate of the silicon carbide single crystal may be 0.1 mm / h or more.

The silicon-based melt composition according to an embodiment may provide a uniform composition even when a crystal growth process is performed, and thereby silicon carbide single crystal of good quality may be obtained.

1 is a schematic cross-sectional view of a manufacturing apparatus used when growing silicon carbide single crystals.
2 is a single crystal image precipitated using the silicon-based melt composition according to the embodiment.
3 is a single crystal image precipitated using a silicon-based melt composition according to a comparative example.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in describing the present disclosure, description of already known functions or configurations will be omitted for clarity of the gist of the present disclosure.

Parts not related to the description are omitted in order to clearly describe the present disclosure, and like reference numerals designate like elements throughout the specification. In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, so the present disclosure is not necessarily limited to the illustrated.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. In the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation. When a portion of a layer, film, region, plate, or the like is said to be "on" or "on" another portion, this includes not only when the other portion is "right over" but also when there is another portion in between.

Hereinafter, a silicon based melt composition according to an embodiment will be described.

The silicon-based melt composition according to an embodiment may include silicon (Si), yttrium (Y), and iron (Fe). The silicone melt composition may be represented by the following formula (1).

Si _a Y _b Fe _c (Equation 1)

In Formula (1), a is 0.4 or more and 0.8 or less, b is 0.15 or more and 0.5 or less, and c is 0.05 or more and 0.3 or less. According to an embodiment, in Formula (1), a may be 0.6 or more and 0.8 or less, b may be 0.2 or more and 0.3 or less, and c may be 0.1 to 0.2 or less.

In other words, in the silicon-based melt composition, the silicon content is at least 40 at% and at most 80 at%, the yttrium (Y) is at least 15 at% and at least 50 at%, and the iron (Fe) is at least 5 at% 30 at% or less. According to the embodiment, the content of silicon in the silicon-based melt composition is 60 at% or more and 80 at% or less, the content of yttrium (Y) is 20 at% or more and 30 at% or less, and the content of iron (Fe) is 10 at% or more. Or 20 at% or less.

When yttrium (Y) is included in the silicon-based melt composition, the solubility of carbon in the melt can be increased. Yttrium (Y) may have a high growth rate of silicon carbide single crystal even at a relatively low temperature (for example, 1800 degrees). Therefore, the single crystal growth process may be performed at a low temperature in the case of containing yttrium. In addition, yttrium (Y) may be advantageously grown in silicon carbide single crystal of high purity because of less incorporation into silicon carbide single crystal.

When yttrium (Y) is included in the silicon-based melt composition in less than 15 at%, the carbon solubility in the silicon-based melt composition is lowered, so that the growth rate of the silicon carbide single crystal may be significantly reduced. In addition, when yttrium (Y) is included in the silicon-based melt composition in excess of 50 at%, polycarbideization of silicon carbide may occur due to excessively high carbon solubility, thereby degrading the quality of silicon carbide crystals. Since the stable growth of silicon carbide single crystal is difficult, the deposition efficiency may be reduced.

When iron (Fe) is included in the silicon-based melt composition of the present application, it is possible to reduce precipitation of impurities due to yttrium. In other words, iron (Fe) may suppress the deposition of yttrium silicide and allow silicon carbide single crystals to be stably deposited for a long time.

When the silicon-based melt composition includes only silicon and yttrium, solid yttrium silicide may be produced at the surface of the melt, and the resulting yttrium silicide changes the concentration of silicon and yttrium in the melt. As a result, the carbon solubility of the surface of the melt, which is the crystal growth region, may change rapidly, resulting in the precipitation of silicon carbide polycrystals or re-dissolution of the grown seed crystals.

According to an embodiment, when the silicon-based melt composition includes iron, precipitation of yttrium silicide may be suppressed. Even if the single crystal growth process proceeds, the composition of the melt can be kept constant, so that the single crystal can be stably obtained.

Iron (Fe) may be difficult to effectively perform the function of suppressing the precipitation of yttrium silicide when included in less than 5 at% in the silicon-based melt composition. In addition, when iron (Fe) is included in the silicon-based melt composition in excess of 30 at%, the carbon solubility of the silicon-based melt composition may be considerably low by excessively suppressing the effect of increasing carbon solubility by yttrium (Y).

The silicon-based melt composition according to one embodiment includes silicon (Si), iron (Fe) which increases carbon solubility in the melt and suppresses the precipitation of impurities including yttrium (Y) and yttrium, which are easy to obtain single crystals even at low temperatures. Better silicon carbide single crystals can be obtained. In addition, the silicon-based melt composition according to one embodiment may provide continuous single crystal growth conditions.

Hereinafter, a method for obtaining silicon carbide single crystal using the above-described silicon-based melt composition will be described with reference to the manufacturing apparatus of FIG. 1. 1 is a schematic cross-sectional view of a manufacturing apparatus used when growing silicon carbide single crystals.

Referring to FIG. 1, the silicon carbide single crystal manufacturing apparatus according to an embodiment may include a reaction chamber 100, a crucible 300 positioned inside the reaction chamber 100, and a seed crystal 210 extending into the crucible 300. In addition, the seed crystal support 230 connected to the seed crystal 210 may include a moving member 250 and a heating member 400 for heating the crucible 300.

The reaction chamber 100 is hermetically sealed including an empty interior space and may be maintained in an atmosphere such as a constant pressure. Although not shown, a vacuum pump and an atmosphere control gas tank may be connected to the reaction chamber 100. After the vacuum chamber and the gas tank for controlling the atmosphere are made inside the reaction chamber 100 in a vacuum state, an inert gas such as argon gas may be charged.

The silicon carbide seed crystal 210 may be connected to the seed crystal support 230 and the movable member 250 to be positioned inside the crucible 300, and in particular, to be in contact with the melt provided in the crucible 300. . This melt may include the above-described silicon-based melt composition and the same description will be omitted.

According to an embodiment, a meniscus may be formed between the surface of the silicon carbide seed crystal 210 and the melt. The meniscus refers to a curved surface formed on the melt by the surface tension generated as the bottom surface of the silicon carbide seed crystal 210 is slightly lifted after contact with the melt. When a meniscus is formed to grow silicon carbide single crystals, the generation of polycrystals can be suppressed to obtain higher quality single crystals.

The silicon carbide seed crystal 210 is made of silicon carbide single crystal. The crystal structure of the silicon carbide seed crystal 210 is the same as that of the silicon carbide single crystal to be manufactured. For example, when the 4H polymorphic silicon carbide single crystal is manufactured, the 4H polymorphic silicon carbide seed crystal 210 may be used. In the case of using the 4H polymorphic silicon carbide seed crystal 210, the crystal growth plane is the (0001) plane or the (000-1) plane, or it is inclined at an angle of 8 degrees or less from the (0001) plane or (000-1) plane. It may be a photographic side.

The seed crystal support 230 connects the silicon carbide seed crystal 210 and the moving member 250. One end of the seed crystal support 230 may be connected to the moving member 250, and the other end thereof may be connected to the seed crystal 210.

The seed crystal support 230 may be connected to the moving member 250 to move up and down along the height direction of the crucible 300. In more detail, the seed crystal support 230 may be moved into the crucible 300 for the growth process of the silicon carbide single crystal or moved outside the crucible 300 after the growth process of the silicon carbide single crystal is finished. In addition, the present specification has described an embodiment in which the seed crystal support 230 moves in the vertical direction, but is not limited thereto and may move or rotate in any direction, and may include a known means for this purpose.

The seed crystal support 230 may be detached from the moving member 250. The silicon carbide single crystal may be coupled to the moving member 250 to be provided inside the crucible 300, and may be separated from the moving member 250 after the growth process of the single crystal is completed.

The moving member 250 may be connected to a driving unit (not shown) to move or rotate the inside of the chamber 100. The moving member 250 may include known means for moving up and down or rotating.

The crucible 300 may be provided inside the reaction chamber 100 and may have an open top shape, and may include an outer circumferential surface 300a and a lower surface 300b excluding the upper surface. The crucible 300 may be of any type for forming silicon carbide single crystals without being limited to the above-described form. The crucible 300 may be filled with a molten raw material such as silicon or silicon carbide powder.

Crucible 300 may be a material containing carbon, such as graphite, silicon carbide, the crucible 300 of such a material itself may be utilized as a source of carbon raw material. Alternatively, but not limited thereto, a crucible of ceramic material may be used, and a material or a source for providing carbon may be provided separately.

The heating member 400 may heat the crucible 300 to melt or heat the material contained in the crucible 300. The heating member 400 may use a resistance heating means or an induction heating means. Specifically, the heating member 400 itself may be formed in a resistance type that generates heat, or the heating member 400 may be formed of an induction coil and formed by an induction heating method of heating the crucible 300 by flowing a high frequency current through the induction coil. . However, it is a matter of course that any heating member may be used without being limited to the method described above.

Silicon carbide manufacturing apparatus according to an embodiment may further include a rotating member (500). The rotating member 500 may be coupled to the lower side of the crucible 300 to rotate the crucible 300. High-quality silicon carbide single crystals may be grown in the silicon carbide seed crystals 210, which may provide a melt having a uniform composition through rotation of the crucible 300.

Hereinafter, the manufacturing method of the silicon carbide single crystal using the above-mentioned silicon type melt composition and the silicon carbide single crystal manufacturing apparatus is demonstrated.

The initial molten raw material including the silicon-based melt composition described above is introduced into the crucible 300. The initial molten raw material may be in powder form, but is not limited thereto. When the crucible 300 includes a carbon material, the initial molten raw material may not include carbon separately, but is not limited thereto. The initial molten raw material may include carbon.

The crucible 300 on which the initial molten raw material is mounted is heated using the heating member 400 in an inert atmosphere such as argon gas. Upon heating, the initial molten raw material in the crucible 300 is changed into a melt containing carbon (C), silicon (Si), yttrium (Y) and iron (Fe).

The melt may be heated to reach a predetermined temperature (eg 1800 degrees), and at a predetermined temperature the carbon solubility in the melt may be saturated. Thereafter, the temperature of the melt in the crucible 300 gradually decreases, and the solubility of carbon in the melt becomes small. When the silicon carbide supersaturated state is in the vicinity of the seed crystal 210, silicon carbide single crystal grows on the seed crystal 210 using this supersaturation degree as a driving force.

As the silicon carbide single crystal grows, the conditions for depositing silicon carbide from the melt may change. At this time, silicon and carbon may be added so as to match the composition of the melt over time to maintain the melt within a predetermined range. The silicon and carbon to be added may be added continuously or discontinuously.

When using the silicon-based melt composition according to an embodiment of the present invention, it is possible to increase the carbon solubility in the melt and to obtain a single crystal even at low temperatures and to suppress the precipitation of impurities containing yttrium, thereby obtaining a silicon carbide single crystal of good quality can do.

Hereinafter, a single crystal precipitated using the silicon-based melt composition according to the Examples and Comparative Examples of the present invention will be described with reference to FIGS. 2 and 3 along with Table 1. 2 is a single crystal image precipitated using the silicon-based melt composition according to the embodiment, Figure 3 is a single crystal image precipitated using the silicon-based melt composition according to the comparative example.

First, raw materials corresponding to Comparative Examples 1 to 8 and Examples 1 to 3 were placed in a graphite crucible, and an Ar gas of 1 atm was evacuated after vacuum evacuation. Thereafter, the mixture was heated to a growth temperature of 1800 degrees (° C.) to prepare a melt, and then maintained at a temperature until the carbon concentration in the melt reached a saturation state. Thereafter, a temperature gradient of −20 ° C./cm was formed along the surface of the melt, and 4H SiC seed crystals were gradually lowered toward the melt surface, followed by contact with each other, for 12 hours. After crystal growth was completed, the seed crystals were pulled from the melt and cooled to compare the growth rate of the single crystal, the precipitation of Yttrium Silicide and the surface state of the single crystal. Carbon solubility was calculated using Factsage, a thermodynamic simulation.

Furtherance Growth temperature
(° C) carbon
Solubility
(%) Crystal growth rate
(mm / h) Yttrium silicide
Precipitation Crystal growth
result Comparative Example 1 Si _0.7 Y _0.3 1800 9.5 X Precipitation Bad surface Comparative Example 2 Si _0.6 Y _0.3 Ni _0.1 1800 4.8 X Precipitation Bad surface Comparative Example 3 Si _0.6 Y _0.3 Al _0.1 1800 4.5 X Precipitation Bad surface Comparative Example 4 Si _0.3 Y _0.6 Fe _0.1 1800 8.6 To 0.02 none Slow growth Comparative Example 5 Si _0.8 Y _0.1 Fe _0.1 1800 2.8 To 0.01 none Slow growth Comparative Example 6 Si _0.3 Y _0.3 Fe _0.4 1800 3.6 To 0.01 none Slow growth Comparative Example 7 Si _0.6 Y _0.37 Fe _0.03 1800 15.3 X Precipitation Bad surface Comparative Example 8 Si _0.6 Y _0.1 Fe _0.3 1800 4.1 To 0.02 none Slow growth Example 1 Si _0.6 Y _0.3 Fe _0.1 1800 14.5 0.40 none Good quality Example 2 Si _0.6 Y _0.25 Fe _0.15 1800 11.75 0.35 none Good quality Example 3 Si _0.6 Y _0.2 Fe _0.2 1800 9.8 0.21 none Good quality

Referring to Table 1, when the silicon-based melt composition includes only silicon and yttrium as in Comparative Example 1, the carbon solubility may be relatively high (9.5%), but it was confirmed that yttrium silicide was precipitated. When yttrium silicide precipitates, it inhibits the growth of single crystals, and thus it was confirmed that the crystal growth result is a poor surface. Nickel (Ni) and aluminum (Al) were added to control the precipitation of yttrium silicide as in Comparative Example 2 and Comparative Example 3, but it was confirmed that yttrium silicide was still precipitated. Nickel and aluminum did not inhibit the deposition of yttrium silicide.

In Comparative Example 4, Comparative Example 5, Comparative Example 6 and Comparative Example 8, it was confirmed that yttrium silicide did not precipitate as the silicon-based melt composition included iron. It was confirmed that precipitation of yttrium silicide was suppressed by iron, and no surface defect was observed in the obtained single crystal. However, in the case of Comparative Example 4, Comparative Example 5, Comparative Example 6 and Comparative Example 8, the crystal growth rate was remarkably slow depending on the content of yttrium and iron included.

When yttrium was contained in 10 at% as in Comparative Example 5, it was confirmed that the effect of increasing carbon solubility by yttrium was insignificant because it was included in a significantly small amount. In Comparative Example 5, the carbon solubility was found to be considerably low, about 2.8%.

Comparative Example 6 is a case in which iron is included at 40 at%, iron suppressed the effect of increasing carbon solubility by yttrium, and in the case of Comparative Example 6, the carbon solubility was about 3.6%, which was considerably low.

Comparative Example 8 is a case where yttrium is contained at 10 at%. In Comparative Example 8, the effect of increasing the solubility of yttrium in carbon is lowered, so that carbon solubility may be significantly lower (4.1%), thereby confirming slow crystal growth.

Comparative Example 7 is a case where iron is contained at 3 at%, in this case it was confirmed that the effect of inhibiting the precipitation of yttrium silicide was insignificant. Although the silicon-based melt composition contained iron, yttrium silicide precipitated and the surface of the single crystal appeared to be poor.

As shown in FIG. 3, the surfaces of the silicon carbide single crystals were found to have poor surface states in Comparative Example 1, Comparative Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 7.

On the other hand, in the case of Examples 1 to 3, the solubility of carbon was 14.5%, 11.75%, and 9.8%, respectively, by including a predetermined yttrium, which is relatively high compared to the comparative examples. The crystal growth rate was also 0.40 mm / h, 0.35 mm / h, 0.21 mm / h was confirmed that the rapid crystal growth is achieved. According to one embodiment of the present invention, the growth rate of the single crystal may be about 0.1 mm / h or more.

In addition, by including the appropriate amount of iron (Fe) it was confirmed that the precipitation of yttrium silicide is suppressed and the quality of the single crystal is good as shown in FIG.

While specific embodiments of the invention have been described and illustrated above, it is to be understood that the invention is not limited to the described embodiments, and that various modifications and changes can be made without departing from the spirit and scope of the invention. It is self-evident to those who have. Therefore, such modifications or variations are not to be understood individually from the technical spirit or point of view of the present invention, the modified embodiments will belong to the claims of the present invention.

100: chamber
210: seed crystal
300: crucible
400: heating member
500: rotating member

Claims (8)

Used in the solution growth method for forming silicon carbide single crystal,
A silicon-based melt composition comprising silicon (Si), yttrium (Y) and iron (Fe), represented by the following formula (1):
Si _a Y _b Fe _c (Equation 1)
In Formula (1), a is 0.4 or more and 0.8 or less, b is 0.15 or more and 0.5 or less, and c is 0.05 or more and 0.3 or less. Preparing silicon carbide seed crystals,
Preparing a silicon-based melt composition comprising silicon (Si), yttrium (Y) and iron (Fe), represented by the following formula (1),
Forming a melt comprising the silicon-based melt composition and carbon (C), and
A method of producing a silicon carbide single crystal comprising the step of obtaining a silicon carbide single crystal on the silicon carbide seed crystal from the melt:
Si _a Y _b Fe _c (Equation 1)
In Formula (1), a is 0.4 or more and 0.8 or less, b is 0.15 or more and 0.5 or less, and c is 0.05 or more and 0.3 or less. In claim 2,
A method for producing silicon carbide single crystals in which yttrium silicide does not precipitate in the step of obtaining the silicon carbide single crystals. In claim 2,
The forming of the molten liquid may include charging the silicon-based melt composition in a crucible and heating the silicon carbide single crystal. In claim 4,
The heating step, the method of producing a silicon carbide single crystal comprising the step of heating the melt to 1800 degrees (° C.). In claim 4,
The melt is a method of producing a silicon carbide single crystal of the carbon solubility is saturated. In claim 6,
And forming a temperature gradient of −20 ° C./cm based on the surface of the melt and then contacting the silicon carbide seed crystal to the surface of the melt. In claim 6,
The growth rate of the silicon carbide single crystal is 0.1 mm / h or more method for producing a silicon carbide single crystal.

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